Traffic management system

ABSTRACT

A real-time traffic management system comprising a main light controller module configured to monitor and control functionality of one or more traffic lights, a master control unit server software application, a network operations control module, and a network watcher application program. The main light controller module communicates with one or more coordinating light controller modules, onsite personnel, and a network operations center. The main light controller uses a camera that detects instances of vehicle demand and provides live images for situational awareness. The main light controller module comprises a global positioning satellite receiver and a light sensor for monitoring ambient lighting conditions. The network watcher application program continuously scans incoming data, monitors performance of all components in the system, and issues alerts and alarms to notify personnel of events or conditions outside of established tolerances.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of U.S. patent applicationSer. No. 13/945,999 filed on Jul. 19, 2013.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to the field of trafficmanagement systems, and more specifically, to a real-time trafficmanagement system for portable or temporary traffic signals that allowsthe user to program and monitor groups of portable traffic signalsystems in real time over the Internet.

2. Description of the Related Art

At present, there are no commercially available products that allow forthe remote and local monitoring and control of groups of mobile trafficlights, including demand-based sequencing. Examples of prior art trafficmanagement systems include: U.S. Pat. No. 3,729,706 (Hein, 1973); U.S.Pat. No. 4,857,921 (McBride et al., 1989); U.S. Pat. No. 6,064,318(Kirchner. III et al., 2000); U.S. Pat. No. 7,333,029 (Hammett, 2008);U.S. Pat. No. 7,633,408 (Yingst et al. 2009); U.S. Pat. No. 7,973,676(Meshkin et al., 2011); and U.S. Pat. No. 8,319,662 (Bontemps et al.2012). None of these systems incorporates the functions and features ofthe present invention, as described more fully below.

BRIEF SUMMARY OF THE INVENTION

The present invention is a real-time traffic management systemcomprising: a main light controller module configured to monitor andcontrol functionality of one or more traffic lights, each traffic lightcomprising a signal head pointing in a direction; a master control unitserver soft-ware application that runs on the main light controllermodule; a network operations control module that is in communicationwith the main light controller module; and a network watcher applicationprogram; wherein the main light controller module is configured tocommunicate with one or more coordinating light controller modules,onsite personnel, and a network operations center; wherein the mainlight controller module uses a camera that detects instances of vehicledemand and provides live images for situational awareness; wherein themain light controller module comprises a global positioning satellitereceiver; wherein the main light controller module further comprises alight sensor for monitoring ambient lighting conditions; wherein thenetwork watcher application program continuously scans incoming data,monitors performance of all components in the system, and issues alertsand alarms to notify personnel of events or conditions outside ofestablished tolerances; and wherein each light controller module has adimming level, and the main light controller module is configured tocontrol the dimming levels of the coordinating light controller modules.In one embodiment, the main light controller module controls the dimminglevels of the coordinating light controller modules based on time ofday. In another embodiment, the main light controller module controlsthe dimming levels of the coordinating light controller modules based oninput from the light sensor.

In a preferred embodiment, the invention is a real-time trafficmanagement system comprising: a main light controller module configuredto monitor and control functionality of one or more traffic lights, eachtraffic light comprising a signal head pointing in a direction; a mastercontrol unit server software application that runs on the main lightcontroller module; a network operations control module that is incommunication with the main light controller module; and a networkwatcher application program; wherein the main light controller module isconfigured to communicate with one or more coordinating light controllermodules, onsite personnel, and a network operations center; wherein themain light controller module uses a camera that detects instances ofvehicle demand and provides live images for situational awareness;wherein the main light controller module comprises a global positioningsatellite receiver; wherein the main light controller module furthercomprises a light sensor for monitoring ambient lighting conditions;wherein the network watcher application program continuously scansincoming data, monitors performance of all components in the system, andissues alerts and alarms to notify personnel of events or conditionsoutside of established tolerances; and wherein at least one of thecoordinating light controller modules comprises a dimming controlfunction that dims a set of heterogeneous signal lamps. Preferably, eachsignal lamp in the set of heterogeneous signal lamps has a ratedvoltage, an actual power consumption and a maximum power consumption;the dimming control function measures the maximum power consumption fora given signal lamp at the rated voltage and uses pulse width modulationto set the actual power consumption for the signal lamp to a desiredlevel; and the actual power consumption is a percentage of the maximumpower consumption of the signal lamp.

In a preferred embodiment, the invention is a real-time trafficmanagement system comprising: a main light controller module configuredto monitor and control functionality of one or more traffic lights, eachtraffic light comprising a signal head pointing in a direction, a mastercontrol unit server software application that runs on the main lightcontroller module; a network operations control module that is incommunication with the main light controller module; and a networkwatcher application program; wherein the main light controller module isconfigured to communicate with one or more coordinating light controllermodules, onsite personnel, and a network operations center; wherein themain light controller module uses a camera that detects instances ofvehicle demand and provides live images for situational awareness;wherein the main light controller module comprises a global positioningsatellite receiver; wherein the main light controller module furthercomprises a light sensor for monitoring ambient lighting conditions;wherein the network watcher application program continuously scansincoming data, monitors performance of all components in the system, andissues alerts and alarms to notify personnel of events or conditionsoutside of established tolerances; and wherein the system furthercomprises an administrative dialog display that allows geographicallydispersed operators and other authorized administrative personnel toexchange messages and record operational events.

In a preferred embodiment, the invention is real-time traffic managementsystem comprising: a main light controller module configured to monitorand control functionality of one or more traffic lights, each trafficlight comprising a signal head pointing in a direction; a master controlunit server software application that runs on the main light controllermodule; a network operations control module that is in communicationwith the main light controller module; and a network watcher applicationprogram; wherein the main light controller module is configured tocommunicate with one or more coordinating light controller modules,onsite personnel, and a network operations center; wherein the mainlight controller module uses a camera that detects instances of vehicledemand and provides live images for situational awareness; wherein themain light controller module comprises a global positioning satellitereceiver; wherein the main light controller module further comprises alight sensor for monitoring ambient lighting conditions; wherein thenetwork watcher application program continuously scans incoming data,monitors performance of all components in the system, and issues alertsand alarms to notify personnel of events or conditions outside ofestablished tolerances; wherein each of the coordinating lightcontroller modules has an input power channel and one or more switchedoutput power channels; and wherein the system further comprises aprocess for detecting anomalies on the input power channel and theswitched output power channels of each coordinating light controllermodule.

In a preferred embodiment, the invention is a real-time trafficmanagement system comprising: a main light controller module configuredto monitor and control functionality of one or more traffic lights, eachtraffic light comprising a signal head pointing in a direction; a mastercontrol unit server software application that runs on the main lightcontroller module; a network operations control module that is incommunication with the main light controller module; and a networkwatcher application program wherein the main light controller module isconfigured to communicate with one or more coordinating light controllermodules, onsite personnel, and a network operations center; wherein themain light controller module uses a camera that detects instances ofvehicle demand and provides live images for situational awareness;wherein the main light controller module comprises a global positioningsatellite receiver; wherein the main light controller module furthercomprises a light sensor for monitoring ambient lighting conditions;wherein the network watcher application program continuously scansincoming data, monitors performance of all components in the system, andissues alerts and alarms to notify personnel of events or conditionsoutside of established tolerances; and wherein the system furthercomprises a process for controlling alternating single lane traffic.

In a preferred embodiment, the invention is a real-time trafficmanagement system comprising: a main light controller module configuredto monitor and control functionality of one or more traffic lights, eachtraffic light comprising a signal head pointing in a direction; a mastercontrol unit server software application that runs on the main lightcontroller module; a network operations control module that is incommunication with the main light controller module; and a networkwatcher application program; wherein the main light controller module isconfigured to communicate with one or more coordinating light controllermodules, onsite personnel, and a network operations center; wherein themain light controller module uses a camera that detects instances ofvehicle demand and provides live images for situational awareness;wherein the main light controller module comprises a global positioningsatellite receiver; wherein the main light controller module furthercomprises a light sensor for monitoring ambient lighting conditions;wherein the network watcher application program continuously scansincoming data, monitors performance of all components in the system, andissues alerts and alarms to notify personnel of events or conditionsoutside of established tolerances; and wherein the system furthercomprises an incremental compass recalibration function that builds andmaintains a library of calibration samples used to derive a set ofconstants required to convert raw compass samples into calibratedazimuth values.

In a preferred embodiment, the invention is a real-time trafficmanagement system comprising: a main light controller module configuredto monitor and control functionality of one or more traffic lights, eachtraffic light comprising a signal head pointing in a direction; a mastercontrol unit server software application that runs on the main lightcontroller module; a network operations control module that is incommunication with the main light controller module; and a networkwatcher application program; wherein the main light controller module isconfigured to communicate with one or more coordinating light controllermodules, onsite personnel, and a network operations center; wherein themain light controller module uses a camera that detects instances ofvehicle demand and provides live images for situational awareness;wherein the main light controller module comprises a global positioningsatellite receiver; wherein the main light controller module furthercomprises a light sensor for monitoring ambient lighting conditions;wherein the network watcher application program continuously scansincoming data, monitors performance of all components in the system, andissues alerts and alarms to notify personnel of events or conditionsoutside of established tolerances; wherein each of the coordinatinglight controller modules has at least two components; and wherein thesystem further comprises a component level control function that has theability to reset an individual component of a light controller modulewhile all other components of the same light controller module remain inan operational state.

In a preferred embodiment, the invention is a real-time trafficmanagement system comprising: a main light controller module configuredto monitor and control functionality of one or more traffic lights, eachtraffic light comprising a signal head pointing in a direction; a mastercontrol unit server software application that runs on the main lightcontroller module; a network operations control module that is incommunication with the main light controller module; and a networkwatcher application program; wherein the main light controller module isconfigured to communicate with one or more coordinating light controllermodules, onsite personnel, and a network operations center; wherein themain light controller module uses a camera that detects instances ofvehicle demand and provides live images for situational awareness;wherein the main light controller module comprises a global positioningsatellite receiver; wherein the main light controller module furthercomprises a light sensor for monitoring ambient lighting conditions;wherein the network watcher application program continuously scansincoming data, monitors performance of all components in the system, andissues alerts and alarms to notify personnel of events or conditionsoutside of established tolerances; wherein the system further comprisesa display device readable by persons in vehicles traveling on a roadwayand capable of displaying content in the form of text and images; andwherein the content of the display device is changed in response totraffic conditions.

In a preferred embodiment, the invention is a real-time trafficmanagement system comprising: a main light controller module configuredto monitor and control functionality of one or more traffic lights, eachtraffic light comprising a signal head pointing in a direction; a mastercontrol unit server software application that runs on the main lightcontroller module; a network operations control module that is incommunication with the main light controller module; and a networkwatcher application program; wherein the main light controller module isconfigured to communicate with one or more coordinating light controllermodules, onsite personnel, and a network operations center; wherein themain light controller module uses a camera that detects instances ofvehicle demand and provides live images for situational awareness;wherein the main light controller module comprises a global positioningsatellite receiver; wherein the main light controller module furthercomprises a light sensor for monitoring ambient lighting conditions;wherein the network watcher application program continuously scansincoming data, monitors performance of all components in the system, andissues alerts and alarms to notify personnel of events or conditionsoutside of established tolerances; wherein the system further comprisesa warning light that flashes yellow while an associated signal is in ayellow or red phase and during a brief interval prior to the associatedsignal turning from green to yellow; and wherein the warning light iscontrolled remotely.

In a preferred embodiment, the invention is a real-time trafficmanagement system comprising: a main light controller module configuredto monitor and control functionality of one or more traffic lights, eachtraffic light comprising a signal head pointing in a direction; a mastercontrol unit server software application that runs on the main lightcontroller module; a network operations control module that is incommunication with the main light controller module; and a networkwatcher application program; wherein the main light controller module isconfigured to communicate with one or more coordinating light controllermodules, onsite personnel, and a network operations center; wherein themain light controller module uses a camera that detects instances ofvehicle demand and provides live images for situational awareness;wherein the main light controller module comprises a global positioningsatellite receiver; wherein the main light controller module furthercomprises a light sensor for monitoring ambient lighting conditions;wherein the network watcher application program continuously scansincoming data, monitors performance of all components in the system, andissues alerts and alarms to notify personnel of events or conditionsoutside of established tolerances; and wherein the system furthercomprises at least one motion detection window that allows a user toallocate motion detection events generated by different motion detectionwindows on a single camera to one or more different signals. Preferably,the at least one motion detection window also allows a user to allocatemotion detection events from different cameras to a single signal.

In a preferred embodiment, the invention is a real-time trafficmanagement system comprising: a main light controller module configuredto monitor and control functionality of one or more traffic lights, eachtraffic light comprising a signal head pointing in a direction; a mastercontrol unit server software application that runs on the main lightcontroller module; a network operations control module that is incommunication with the main light controller module; and a networkwatcher application program; wherein the main light controller module isconfigured to communicate with one or more coordinating light controllermodules, onsite personnel, and a network operations center; wherein themain light controller module uses a camera that detects instances ofvehicle demand and provides live images for situational awareness;wherein the main light controller module comprises a global positioningsatellite receiver; wherein the main light controller module furthercomprises a light sensor for monitoring ambient lighting conditions;wherein the network watcher application program continuously scansincoming data, monitors performance of all components in the system, andissues alerts and alarms to notify personnel of events or conditionsoutside of established tolerances; and wherein the system furthercomprises a jump command that instructs the main light controller moduleto terminate a current traffic phase, jump to an indicated trafficphase, and continue sequencing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of the system architecture of the present invention.

FIG. 2 is a diagram of a typical installation of the onsite componentsof the present invention and other hardware to which they are connected.

FIG. 3A is a diagram of a sample deployment scenario for the presentinvention involving a one-lane closure.

FIG. 3B is a diagram of a sample deployment scenario tor the presentinvention involving a three-way intersection.

FIG. 3C is a diagram of a sample deployment scenario for the presentinvention involving a four-way intersection.

FIG. 3D is a diagram of a sample deployment scenario for the presentinvention involving a four-way intersection with four left turn bays.

FIG. 4 is a flow diagram of the components of the light controllerserver software.

FIG. 5 is a flow diagram of the user command processing of the lightcontroller server software.

FIG. 6 is a flow diagram of the automated generator control processingof the light controller server software.

FIG. 7 is a screenshot of the operator's console display and a diagramof its keypad layout.

FIG. 8 is a diagram of the button layout of the handheld remote control.

FIG. 9 is a flow diagram of the camera configuration procedure.

FIG. 10 is a flow diagram of the components of the master control unitserver software.

FIG. 11 is a flow diagram of the user command processing of the mastercontrol unit server software.

FIG. 12 is a flow diagram of the auto discovery processing portion ofthe master control unit.

FIG. 13 is a screenshot of the main display of the master control unit.

FIG. 14 is a screenshot of the map display of the master control unit.

FIG. 15 is a screenshot of the setup display of the master control unit.

FIG. 16 is a screenshot of the onsite signal summary portion of thesetup display of the master control unit.

FIG. 17 is a screenshot of the super remote application of the mastercontrol unit.

FIG. 18 is a flow diagram of the components of the archiving proxyserver software.

FIG. 19 is a flow diagram of the archiver process of the archiving proxyserver software.

FIG. 20 is a flow diagram of the user command processing of thearchiving proxy server software.

FIG. 21 is a screenshot of the consolidated summary display generated bythe archiving proxy server software.

FIG. 22A is a first sample strip chart display generated by thearchiving proxy server software.

FIG. 22B is a second sample strip chart display generated by thearchiving proxy server software.

FIG. 22C is a third sample strip chart display generated by thearchiving proxy server software.

FIG. 23 is a flow diagram of the network watcher application.

FIG. 24 is a flow diagram of the MCU dimming control process.

FIG. 25 is a flow diagram of the LTC dimming control process.

FIG. 26 is a screenshot of the administrative dialog display of thearchiving proxy server.

FIG. 27 is a flow diagram of the LTC per-channel power monitoringprocess.

FIG. 28 is a flow diagram of the alternating single lane traffic controlprocess.

FIG. 29 is a flow diagram of the incremental compass recalibrationprocess.

FIG. 30 is a flow diagram of the LTC component level control process

FIG. 31 is a diagram of the system architecture of the present invention

FIG. 32 is a screenshot of the onsite signal summary portion of thesetup display of the master control unit

FIG. 33 is flow diagram of the user command processing of the mastercontrol unit server software.

FIG. 34 is a sample strip chart display generated by the archiving proxyserver software.

DETAILED DESCRIPTION OF INVENTION

A. Overview

The present invention is a real-time traffic management system forportable or temporary traffic signals that allows the user to programand monitor groups of portable traffic signal systems in real time overthe Internet. Once the light controller (LTC) module is installed on aportable traffic signal, the network operations control (NOC) module,which is at a fixed geographic location, is able to establishcommunications with the control module, verify that all equipment isworking properly, and program the system to control traffic according tothe desired program. Through the use of live video feeds of the trafficapproaching each signal, the control center is able to establish vehicledemand detection locations fir each lane that the signals arecontrolling and utilize these vehicle arrival events as part of theprogram. The live video also allows our control center to monitor thetraffic approaching each signal to verify that the program isefficiently handling traffic flows and to provide remote situationalawareness of system operation.

The ability to detect vehicle arrival events in multiple lanes oftraffic in the same direction (left turn, through traffic and rightturn) and to program and control each lane on separate phases gives thesystem the flexibility and ability to be used in complex applicationsnot previously possible with temporary signal systems. Live adjustmentscan be made to the program to improve the efficiency of the traffic flowor to manually control each signal if needed in the event of anemergency. All data arriving at the control center, including textstatus data and images (both still images and videos), is permanentlyarchived for both immediate real-time retrieval and also after-the-factreview. (As used herein, the term “images” includes both still imagesand videos.) At the same time, the network watcher application programcontinuously scans the incoming data, monitoring the performance of allthe components of the system, and issues alerts and alarms to notifycontrol center personnel and to update their displays, as well as tonotify designated project personnel should any events or conditionsoccur that are outside established tolerances.

The present invention provides for remote control of trafficintersection without the need for a continuous onsite presence ofpersonnel such as flaggers. Instead, the present invention requiresminimally trained onsite personnel only during the setup and tear-downactivities and whenever direct intervention is required. Thefunctionality and features of the present invention are described morefully below with reference to the figures.

B. Detailed Description of the Figures

FIG. 1 is a system architecture diagram for the invention. The lightcontroller (LTC) 101 is a computer-based controller module capable ofmonitoring and controlling the functions of typical traffic light, aswell as communicating with other LTCs 110, onsite personnel 114, and thenetwork operations center (NOC) 124. The LTC can control the individualsignal lamps comprising two or more independent traffic signal heads102, 103, two or more walk/don't walk signals 104, and two or more walkbuttons 105. The LTC uses a camera 106 pointed in the direction oftraffic approaching the signal to detect instances of vehicle demand andalso to provide images used for situational awareness. (Note that thecamera 106 is either integral to the LTC hardware or a separate hardwarecomponent that connects to the LTC.) The LTC has specialized circuitry(hardware) 107 that is capable of monitoring its supply voltage 108, andthe LTC uses this information to control an attached generator/chargingsystem 109.

The LTC can communicate with one or more similarly configuredcoordinating LTCs 110 in the vicinity using two or more radios 111operating on two or more non-overlapping radio frequency bands. The LTCdoes not communicate (nor attempt to communicate) with othernon-coordinating LTCs 112 in the vicinity (e.g., those operating atdifferent intersections or under different ownership). The LTCcommunicates wirelessly via an operator's console 113 with onsite fieldservice personnel 114, providing a secure monitor and control interfaceto authorized personnel. The LTC monitors its location through the useof a global positioning satellite (GPS) receiver 115 and attendant GPSsatellites 116. The LTC uses a light sensor 117 to monitor the ambientlighting conditions 118 and uses this information to optionally dim thetraffic signals lamps under its control using its dimmer circuitry 119.The LTC uses a compass 120 to detect the direction to magnetic north 121to determine the direction in which the traffic signal head is pointing.LTC is also capable of maintaining an uplink to the Internet 122 througha variety of common methods, including a cellular network, localwireless access such as WiFi, and a traditional wired Internetconnection. The LTC uses the uplink primarily to receive commands fromand report status to the archiving proxy server (APS) 123 at the NOC 124but will also provide similar access to other authorized remote users125 via the administrative displays 126 for redundancy in the event ofthe loss of the NOC 124. The APS 123 is preferably fixed in place onsiteand not mobile (it has a reliable connection to the Internet).

The NOC is a set of computers, software, displays, and personnel thatcontinuously monitors the operation of all LTCs. The APS activelyrequests status from each Master Control Unit (MCU) and pictures fromeach camera and archives all responses for immediate and long-termretrieval in either the status or image archives 127 and 128. It alsoresponds to indirect status and image requests from authorizedadministrative users 125 via administrative displays 126 just as ifthose users were directly connected to the LTC; similar requests fromclient users 129 via client displays 130; and similar requests frompublic users 131 via the public displays 132. The APS also acts to relaycommands from authorized users to LTCs in the field, providing securemonitor and control access to the intersections from anywhere in theworld.

The network watcher 133 monitors the stream of data flowing from theLTCs to the APS, looking for out-of-tolerance conditions (e.g., lowvoltage or radio link quality issues). When such conditions aredetected, the network watcher sends notifications either via email ortext message to the set of address on a preconfigured list. The networkwatcher also maintains a series of graphs showing system parametervalues (e.g., line voltage or radio link quality) in the recent past.

FIG. 2 is a diagram showing the LTC 201 in the environment in which itoperates in the work zone. A signal trailer upon which the LTC ismounted typically comprises: wheels and/or stabilizers 202 to provide astable horizontal platform; a solar charging system 203; batteries andan optional generator and charging system 204; an arm 212 to support twostandard signal heads 205; an optional monitor lamp 206; an optionalleft turn arm 207 and signal head 208; one or two optional walk/don'twalk signals 209 to control pedestrian traffic with and against the flowof traffic; one or two optional walk buttons 210 to indicate pedestriandemand with and against the flow of traffic; and storage and a powersupply for the operator's console 211. The electrical system powers theLTC, while the LTC conditionally supplies dimmed power to all lamps andsignals, accepts inputs from the optional walk buttons, and optionallycontrols the generator and associated charging system.

The LTC's camera records images for retrieval by the APS or otherauthorized users. It also detects motion events and reports them to theMCU. The GPS device provides location and timing information and compassrecords the azimuthal direction in which the signal head is pointing.Multiple radios on at least two different unlicensed radio bands areused to provide redundant communication routes in case of adverseenvironmental conditions or equipment failure. The MCU runs on the LTC101, which coordinates the activities of its own signal hardware as wellas that of other LTCs and, where Internet connectivity is available,responds to commands from the APS and authorized remote users.

FIGS. 3A-3D depict four sample scenarios, among many others, in whichtraffic signals equipped as in FIG. 2 might be deployed to controltraffic in a safe and effective manner and to also provide for remotemonitor and control. The lane closure scenario in FIG. 3A shows how twotraffic signals equipped with the invention can be used to controltwo-way access to a single lane of traffic (to be configured as twophases, with one signal on each phase). The three-way intersectionscenario in FIG. 3B shows how three traffic signals equipped with theinvention can be used to control three-way intersections (two phases,with the eastbound and westbound signals on the main phase, and theremaining southbound signal on a second phase). The four-wayintersection scenario in FIG. 3C shows how four traffic signals equippedwith the invention can be used to control four-way intersections (twophases, with two signals on each phase). The four-way intersection withfour left turn bays scenario in FIG. 3D shows how four signals equippedwith the optional left turn signal arms and heads can be used to controltraffic at such an intersection, where the phases can be defined in anumber of ways (e.g., with a north-south phase, an cast-west phase, andtwo separate left turn phases, or with a north-south phase, anorth-south left turn phase, an eastbound phase with protected leftturn, and a westbound phase with protected left turn).

In addition to the pictured scenarios, other scenarios—such as for pilotcar operations or for crosswalk applications—are possible because thesystem can support an essentially unlimited number of LTCs on a givensite, organized in an unlimited number of phases, with an unlimitednumber of signals per phase.

FIG. 4 is a flow chart of the application functions within the LTCserver. The LTC server is a control application with a web serverinterface, allowing it to both accept commands from and return responsesto user applications via a network connection while performing itscontrol function in the background. The mainline of the LTC server isorganized as a loop that repeats for as long as the computer remains inoperation and is depicted on the left in this figure. In response to anetwork user command, the server portion of the software spawns separatethreads to service them as depicted on the right in this figure.

At power up 401, the various electrical components of the LTC powerthemselves up, and the LTC computer's operating system bootstraps itselfinto operation and eventually starts up the LTC server. After startup,the server initializes itself 402 by reading its configuration file todetermine the details of its installation (e.g., whether a left turnsignal head is present, whether a generator is present, theidentification of the ‘learned’ handheld remote control, if any),determines the unique LTC identifier, establishes communication with theoperator console, establishes communication with the radio modemhardware, if so configured, and registers with the server software to benotified of certain web-based addresses that form the basis of the LTC'snetwork interface.

In order to facilitate the MCU's auto discovery function, which isdescribed below, the LTC will also transmit a beacon message duringinitialization containing its identifier and other status information,notifying all MCUs in the radio neighborhood of its presence andavailability for service. Once initialization is complete, the serverenters the server loop by first establishing a mutual exclusion lock onthe data shared with the server threads 403, essentially locking out thenetwork command interface and precluding data corruption from multipleprocesses writing to the same storage area. Once the lock is obtained,the radio modem is accessed for any valid received messages addressed tothis LTC 404, which may be commands from the MCU, from the handheldremote control, or other authorized personnel. LTC commands, theprocessing of which are described in FIG. 5, are acted upon and thenacknowledged with the format of the acknowledgement being specific tothe type of the originator (MCU, handheld remote, or other user).

Once the radio modem processing is complete, the operator's consoledisplay is updated, and any keystrokes are serviced 405. The operator'sconsole display and keypad layout is described in FIG. 7. The consoledisplay consists of basic LTC status information. The keypad can be usedto issue a limited set of LTC commands (e.g., start, stop, start left,stop left, mode change, auto/local select, learn) and, if so configured,a limited set of MCU commands (red, flash, and sequence).

Once the operator's console has been serviced, any learn mode processingis performed 406. While in learn mode, the LTC scans the received radiomessages for separate start and stop commands that are tagged with thehandheld remote ID, indicating that they originated from the samehandheld remote. If such a pair is received before the learn mode timerexpires, the identifier of the originating handheld remote is ‘learned’by the LTC, and the LTC updates its configuration file accordingly,making the change permanent across power cycles. Once learn modecompletes, successfully or not, the LTC enters standard mode, cycles tored, and awaits further command.

Once learn processing is complete, the LTC interrogates the on-boardhardware for faults such as a failed signal lamp 407. If any such faultsare detected, the LTC begins reporting a hardware fault in the statusportion of all subsequent acknowledgement messages notifying the senderof the condition. The LTC will continue to report the error conditionuntil the fault has cleared and remained cleared for a configurable timeperiod, nominally 15 minutes, giving users such as the MCU and theAPS-based applications (such as the network watcher) ample opportunityto take any necessary actions. Next, the supply voltage, temperatureinside the LTC, GPS location and compass headers are sampled 408. Thisdata is included in the status portion of subsequent acknowledgementmessages.

At this point, if so equipped, the generator and charging system (whichis explained in more detail in FIG. 6) is serviced 409. This processinvolves attempting to start the generator when the line voltage isbelow the configured value, detecting when the generator is running andpresumably charging the batteries, attempting to stop the generatorafter a fixed and configurable run time has elapsed or when socommanded, detecting with the generator has stopped running, anddetecting when the generator is low on fuel. Once any generatorservicing is complete, any pending red light or flasher mode phasetransitions are handled 410. A pending red light occurs when the LTC hastransitioned either the standard or left rum signal head into the yellowphase and has scheduled a phase change to red at a future time. If thattime has passed, the LTC will transition the appropriate signal head tothe red phase. Similarly, when in flasher mode, the LTC will schedule aphase transition, on-to-off or off-to-on, to occur twice a second. TheLTC uses the timing information derived from the GPS signal tosynchronize flasher mode phase transitions to the atomic clock at theUnited States Naval Observatory in Washington, D.C. In so doing, the LTCsynchronizes flasher mode phase transitions of all coordinating signals.The LTC may be configured to illuminate the selected signal lamp duringeither the top half or the bottom half of the second, allowing signalsin one phase to flash alternately with the signals in a second phase.When the timer expires, the LTC will perform the necessary phase changeby turning the selected signal lamp on or off as need be and thenschedule the next change to occur one half second hence.

Once the pending red light or flasher mode phase transitions handling iscomplete, the LTC will, on a specified interval and if networkconnectivity is available, attempt to report its performance directly tothe APS, bypassing the MCU 411. Once the latter step is complete, theLTC will maintain its log files on a specified interval 412. Any logfiles larger than a specified size will be rotated (i.e., the currentcontents will be moved to a backup file, and any subsequent log messageswill be directed to a new file). The backup file will be offloaded tothe APS, if possible, and then deleted from the system. Once theseprocesses complete, the LTC releases the mutual exclusion lock 413 andgoes to sleep for a brief period of time 414, allowing external users toaccess to the server.

Where communications exist, authorized users can issue network commandsdirectly to the LTC server. If such a command arrives while the LTC issleeping 415, the server portion of the software spawns a thread toservice each request 416. The first step in processing a user request isto establish a mutual exclusion lock on the shared server data 417. Oncethe lock is obtained, the user LTC user command is executed andacknowledged 418. In step 418, the set of commands recognized by theserver on the network interface is identical to the set recognized instep 404, and the processing of the user commands is as described inFIG. 5. Once the LTC user command processing is completed, the mutualexclusion lock is released 419, and the server thread terminates 420.

FIG. 5 is a flow diagram that shows the processing of the LTC commands.Processing of a command starts 501 when the routine is called from themainline of the LTC executive or as the result of a network usercommand. If the command is a request for status 502, then anacknowledgement containing the comprehensive LTC status is formulatedand sent back to the originator 503 and control is returned to thecalling routine 504. If the command is a mode change command 505, and ifremote commanding is not locked out and if the command contains thecorrect MCU ID, the operating mode of the LTC is changed accordingly506. For standard mode, the LTC terminates other operating modes, cyclesthe standard signal head to the red phase and, if so equipped, cyclesthe left turn signal head to the red phase as well. In either case, ifthe signal head in question is not already in the red phase, the signalwill be transitioned to the yellow phase, and a pending red timeout willbe set. For flasher mode, the LTC terminates other operating modes and,in the case of flash yellow, transitions the standard and, if soequipped, the left turn signal head, to the yellow phase. In the case offlash red mode, the LTC will briefly transition the standard signal headand, if so equipped, the left turn signal head, to the yellow modebefore initiating red flash mode.

For pilot car mode, the left signal head, if so equipped, is disabled,and the standard signal head is transitioned to red as described forstandard mode. As with all remaining commands, once the processing ofthe command is complete, an acknowledgement containing LTC status issent to the originator, and control is returned to the caller. If thecommand is a start or stop command for the standard or left turn signalheads 507, and if remote command is not locked out and if the commandhas the correct MCU ID, the phase of the signal is changed as commanded508.

While the LTC is operating in standard mode, a start command will causethe LTC to transition the standard signal head to the green phase, and astart left command will do the same for the left turn signal head.Likewise, a stop command will cause the LTC to cycle the standard signalhead to the red phase, through the configurable duration yellow phase,as necessary, and a stop left command will do the same for the left turnsignal head. While the LTC is operating in the flasher mode, a startcommand will cause the LTC to change the standard signal head's flashcolor to yellow, and a stop command will cause it to change the standardsignal head's flash color to red. Similarly, while in flasher mode, astart left command will cause the LTC to change the left turn signalhead's flasher color to yellow, and a stop left command will cause it tochange the left turn signal head's flasher color to red.

While the LTC is in pilot car mode, a start command will cause the LTCto either change the main signal head phase to green and start acountdown timer or, if the signal was already in the green phase, add afixed and configurable number of seconds to the already runningcountdown timer. Should the timer expire, the LTC will transition thestandard signal head phase from green to red, through a yellow phase ofconfigurable duration. While the LTC is in pilot ear mode, a stopcommand will also cause the LTC to transition the standard signal headto red phase, just as if the timer had expired. While the LTC is inpilot car mode, start left and stop left commands will be ignored.

If the command is a learn command 509, the LTC enters learn mode 510 andbegins to listen for a pair of commands (a start and a stop command)originating from the same handheld remote control within a certaintimeout period. If the command is a remote command 511 and has thecorrect MCU ID, then the LTC examines the parameters and determineswhether remote commanding is being enabled (i.e., commanding by the MCUis to be allowed) or disabled (MCU commanding to be locked out) andchanges the state operations accordingly 512. If the command is agenerator control command 513, the LTC parses the parameters(enable/disable, threshold voltage, run time, quiet hours start andend), saves the details to the configuration file, and then executes thespecific generator control command 514: enable, which turns on thegenerator control function disable, which turns off the generatorcontrol function; run, which starts a generator run sequence; or stop,which terminates any ongoing generator run sequence. If the command is aleft turn enable/disable command 515, then the LTC parses the parametersto determine whether the left turn signal head is being enabled ordisabled, updates the configuration file, and modifies processingaccordingly 516. If the command is a reboot command 517, then the LTCissues a time-delayed reboot command to the system 518, allowing thecommand to be acknowledged before the reboot begins. If the command wasnot a reboot command, then the set of recognized LTC commands isexhausted, a negative acknowledgement message is formulated and sent tothe originator 519, and control is returned to the caller.

FIG. 6 is a flow diagram depicting the automated generator controlprocess. Processing, begins when invoked by the main line of the lightcontroller server 601 and continues with testing whether the automatedgenerator control function is enabled 602. If it is not, processing iscomplete, and control is returned to the caller 603. If control isenabled, then the configurable quiet hours (a period of time in whichthe generator should not be run) is compared against the system clock todetermine whether quiet hours are in effect 604. If quiet hours are ineffect, a check is made to determine whether the generator is running605. If the generator is running, the LTC will try to stop the generator606 by applying power briefly to the generator stop circuit, after whichcontrol is returned to the caller. If quiet hours are not in effect andthe generator is not being run, a test is made to determine whether thesupply voltage is less than the configurable threshold voltage 607. Ifso, then the LTC will attempt to start the generator 608 by applyingpower briefly to the generator start circuit. Otherwise, a test is madeto determine whether the LTC is in the process of starting the generator609. If so, a test is performed to determine whether the generator isproducing alternating current 610, and, if so, the LTC will declare thegenerator to be running 611. If the generator is not running, a timer isconsulted to determine whether a timeout has occurred 612. If a timeouthas occurred, a test is made to determine whether too many consecutivetimeouts have occurred 613. If not, the LTC will retry the start process614 by again applying power briefly to the generator start circuit.

If all start retries have been exhausted, the LTC declares the generatorto be disabled 615, effectively precluding further processing until thegenerator is manually re-enabled. If the LTC was not trying to start thegenerator, a test is made to determine whether the generator is beingrun by the LTC 616. If so, a test is made to determine whether theconfigurable generator run time has elapsed since the generator wasdeclared to be running 617. If so, the LTC will attempt to stop thegenerator by briefly applying power to the generator stop circuit 618.

If the generator was not being run by the LTC, a test is then made todetermine whether the LTC is attempting to stop the generator 619, and,if so, a test is made to determine whether the generator is producingalternating current 620. If the generator is not producing alternatingcurrent, the LTC declares the generator to be stopped 621. If thegenerator is producing alternating current, a test is made to determinewhether a timeout has occurred since the last attempt to stop thegenerator 622, and, if so, a test is made to determine if too manyconsecutive timeouts have occurred 623. If not, the LTC will againattempt to stop the generator 624 by briefly applying power to thegenerator stop circuit. If all stop retries have been exhausted, the LTCdeclares the generator to be disabled 625, effectively precludingfurther processing until the generator control function is manuallyre-enabled. After this, control is returned to the caller 603.

FIG. 7 is a depiction of the LTC's operator's console, showing both thedisplay portion 701 and the keypad 702. The display includes supplyvoltage, current time, operating mode, standard signal head phase, andthe MCU lock out state (auto vs. local) and software identification.

Reference numbers 703 through 709 are keys on the operator's consolekeypad by which onsite personnel can send commands to the LTC, theeffect of which is identical to similar commands received from otherinterfaces (e.g., the network or radio modem interfaces). When the userpresses the start 704, stop 703, start left 706, or stop left keys 705,the LTC acts upon them in the manner described above. When the mode key707 is pressed, it causes the LTC to cycle through operating modes inthe following sequence: standard, flasher, pilot car, and then back tostandard. Pressing the auto key 708 causes the LTC to toggle the mastercontrol lock out mode between auto (MCU commanding allowed) and local(MCU commanding locked out). Pressing learn key 709 causes the LTC toenter the learn mode and to prompt the user to push specific buttons onthe handheld remote control whose identification is to be learned.

Reference numbers 710 through 714 are keys on the operator's consolekeypad by which onsite personnel can send commands to the MCU, therebyeffecting the operation of all signals at the intersection. Pressing thewalk with 710 or walk against 711 key will cause the LTC to send thecorresponding event notification to the MCU, notifying it of user demandeither for traffic moving parallel with traffic approaching the trafficsignal (walk with) or for traffic moving across traffic approaching thetraffic signal (walk against). Pressing the red key 712 will cause theLTC to send a ‘mode change red’ command to the MCU, which, ifsuccessful, will cause all traffic signals at the intersection to cycleto the red phase. Pressing the flash key 713 will cause the LTC to senda ‘mode change flash’ command to the MCU, which, if successful, willcause all traffic signals at the intersection to change to flash mode,the color of which is determined by the saved master controlconfiguration. Pressing the sequence (‘seq’) key 714 will cause the LTCto send a ‘mode change auto’ command to the MCU, which, if successful,will cause the MCU to begin automatically sequencing the phases of thetraffic signals at the intersection according to its savedconfiguration.

FIG. 8 shows the handheld remote control 801 and its push button layout.Reference numbers 802 through 805 represent buttons that, when pressedby onsite personnel, cause the handheld remote to transmit a commandcode containing the handheld remote control's unique ID, correspondingbutton code, and checksum, which, if received by a radio modem on an LTCthat is configured to accept commands containing the control's uniqueID, will cause the LTC to execute the corresponding command (e.g. stop802, start 803, stop left 804, or start left 805) as if that command hadbeen received from the network interface or operator's console.

FIG. 9 is a flow chart showing the LTC camera configuration procedure.The camera configuration procedure is started 901 by control centerpersonnel whenever the camera arrives at a new location. The camera isconfigured 902 to have a name that is related to the name of the LTC inwhich it is installed and to know where to find the current time and inwhich time zone it is installed. The camera's image is cropped 903 toframe the approaching traffic and to discard portions of the image notrelated to traffic control so as to reduce the amount of data to betransferred to the NOC. The camera is also configured to shrink theimage in each dimension by an inverse power of two (usually one-halt) inorder to further reduce the number of pixels required to represent theimage and further reduce uplink bandwidth.

Once the scene is framed, an event detection window is defined 904 interms of location within the frame and in terms of othercamera-dependent parameters relating to various threshold values thatmust be crossed for the camera to declare a vehicle arrival event tohave taken place. Once a motion window is defined, the action to betaken upon such an event is defined 905. The action will typically be tocontact the MCU and report the event along with an identifier by whichthe MCU can identify the signal at which the motion is detected. Ifthere are more motion detection windows to be defined 906, the previoussteps 904, 905 are repeated. Once all windows are defined, the processis complete 907.

For a number of reasons involving viewing geometry and traffic flows,the motion detection process may falsely trigger on traffic moving awayfrom the traffic signal or may trigger multiple times for a singlevehicle. To account for this, in most cases the MCU only considersmotion detection events for signals that are already in the green phaseand uses the occurrence of such event to extend the duration of thecurrent green phase up to the maximum allowable time. This has theeffect of ignoring the false triggers for traffic moving away from thesignal (because the signal is presumably in red) and has the effect ofusing only the final event when a vehicle generates multiple events.Although the system records the number of vehicle detection events, itmake no decisions based upon the absolute number of such events or therates of their occurrences.

FIG. 10 is a flow chart of the application functions within the MCUserver software, which is a software program running on one of the LTCsin an intersection and which exercises control over all coordinatingonsite LTCs. The MCU server software is a control application with webserver functions, allowing it to act as a server by accepting commandsfrom, and returning responses to, authorized users and user applicationsvia a network connection and also to act as an application controlling areal-time process. It is organized as a loop that repeats for as long asthe computer remains in operation, as depicted on the left in thisfigure, and a series of separate threads that are spawned by the serverportion of the software in response to network user commands, asdepicted on the upper right in this figure.

At power up 1001, the various electrical components of the MCU powerthemselves up, and the MCU's operating system bootstraps itself intooperation and eventually starts up the MCU server software. Afterstartup, the server initializes itself 1002 by reading its configurationfile, which may contain: a list of LTCs; a set of two or more phasedefinitions, each consisting of a flow name, a maximum green duration(green max), a minimum green duration (green min), the green timeincrement (green idle), yellow phase duration (yellow), time to clearthe intersection (clear time) and a set of LTC's assigned to that phaseand the cameras associated with each; and an operating mode (e.g.,standby, red, flash, sequencing). If no configuration file is found, theMCU will enter standby mode, passively listening to radio traffic toidentify onsite LTCs and also waiting for the discovery process toproduce the definitive list. As part of the initialization process, alist of zero or more LTC commands are composed that taken togetherimplement the mode of operation described by the configuration file. Inthis way, the operating state of the MCU, and the intersection itcontrols, is persistent across reboots and power cycles. As part of theinitialization process, the MCU also launches the automated discoverymechanism (described below in FIG. 12).

Once initialization is complete, the server enters the server loop byfirst establishing a mutual exclusion lock on the data shared with theserver threads 1003, essentially locking out the network commandinterface and precluding data corruption from multiple processes writingto the same storage area. Once the lock is obtained, any pending LTCmessages are received 1004. Each pending message is processed in theorder received and is either an acknowledgement of a previous MCUcommand, a command from an LTC to the MCU, or a message that isunrelated to this MCU's activities (e.g., errant transmissions).Acknowledgements of previous commands are checked against any pendingunacknowledged command, and, if a match is found, the pending command islabeled a success, and a countdown to the next command transmissionbegins. Any commands from the LTCs to the MCU are acted upon, if valid.Any unrelated message traffic is used to maintain a list of onsitesignals, wherein if the message identifier corresponds to a known LTC(i.e., an LTC authorized to be operated at this intersection and by thisclient user) and that LTC is not already on the list of onsite LTCs, itwill be added to the list and included in any subsequent MCU statusmessages. This is a critical piece of the automatic discovery mechanismand works with the LTC's beacon function to allow the master controllerto reliably detect the presence of LTCs not actively being controlled.

Once this processing is complete, LTC timeouts are handled 1005, whereinany LTC commands that have remained unacknowledged in excess of aconfigurable time period are declared to have failed, and after whichthe failure count is incremented and checked against a maximum failurecount. If the failure count has been reached, the MCU changes to thealternate radio band, resets the retry counters, and restarts thetransmission process. If the failure count has reached the maximum andall radio bands have been exhausted, the MCU will declare a fault,deeming itself not to be in control of the intersection, make theconfigured notifications, and restart the command sequence from thebeginning in order to re-establish, and subsequently maintain, controlof the intersection. Once the timeout processing is complete, anyscheduled LTC commands are transmitted 1006. The current time iscompared against the next scheduled command transmission time, and, iffound to be less, the next scheduled command is sent, addressed to theintended LTC, and the acknowledgement countdown timer begins.

Once that processing is complete, any green idle events are detected andhandled 1007. A green idle event occurs when, during sequencingoperations, the MCU detects that the current phase has been active inexcess of the configurable minimum green time, but less than the maximumtime, and there have been no vehicle arrival events attributed to anysignal on that phase for more than the configurable green idle time.When a green idle event occurs, the master controller simply advances tothe next command in the command sequence and, by doing so, prematurelyterminates the current traffic phase and advances to the next, passingcontrol of the intersection from an idle phase to one that perhaps hastraffic waiting to be serviced.

Once that processing is complete, and if the MCU is operating in smartpilot car mode, any smart pilot car mode processing 1008 is performed,wherein a check is made for the reception of any commands from ahandheld remote control containing an identifier for which the MCU hasbeen configured to respond. The only relevant commands originating fromthe handheld remote are: a start command, which causes the MCU to eithercommand the associated signal to green and schedule the end of thatphase for a configurable number of seconds hence or, if the signal isalready in the green phase, add a configurable number of seconds (thepilot car green idle time) to the scheduled end of the current greenphase; and a stop command, which causes the MCU to command the LTC toimmediately cycle to the red phase.

Once that processing is complete, the auto discovery function is handled1009, wherein information about any LTCs detected by the independentauto discovery process is received and integrated with the MCU'sexisting list of active controllers and monitors, and any newlydiscovered units are added to the list for subsequent reporting andusage. After this step, the list of active onsite LTCs is examined forany entries whose time of last contact is greater than a configurablevalue. Any such entry that is not part of the active configuration(i.e., is not an LTC being actively commanded) is deemed to beunreachable and is removed from the list (and removed as a selectionoption from any MCU user applications).

Once that processing is complete, and on a periodic basis, the MCUsamples its supply voltage, operating temperature and GPS location 1010for subsequent reporting to the APS and use by the network watcher. Oncethat processing is complete, and on a periodic basis, the MCU serversoftware reports certain performance statistics to the APS 1011 in orderto paint a fuller picture of system operation. Once that processing iscomplete, any open log files are checked against a configurable maximumlength and, if too large, are rotated 1012 in a fashion similar to thatdescribed in FIG. 4 (reference number 412).

Once these processes complete, the MCU server software releases themutual exclusion lock 1013 and goes to sleep for a brief period of time1014, allowing external users to access to the server. Where a networkconnection exists, authorized users can issue network commands directlyto the MCU server software. When a user command arrives, it is detectedby the server 1015, which spawns a thread to service that request 1016.The first step in processing a user request is to establish a mutualexclusion lock on the shared server data 1017. Once the lock isobtained, the MCU server software command is executed 1018 andacknowledged, and any requested data is returned to the originator. Theset of commands recognized by the server is described in FIG. 11. Whenprocessing is complete, the mutual exclusion lock is released 1019, andthe server thread terminates 1020.

FIG. 11 is a flow diagram that shows the processing of the MCU commandsby the MCU server software. Processing of a command starts 1101 when theroutine is invoked by the server software as the result of a usercommand. If the command is a request for status 1102, then anacknowledgement containing the MCU status, which includes the mostrecent status messages from all onsite LTCs as well as detailedinformation about current and recent MCU operations, is formulated andsent back to the originator 1103, and control is returned to the callingroutine 1104, as is the case for all successful commands. If the commandis an intersection configuration 1105, then the MCU server softwareparses and validates the message parameters, which include intersectionname, phase definitions, and smart pilot car timing, and, if theparameters are found to be valid, saves them to the configuration fileand modifies its operations to reflect the command parameters 1106. Ifthe command is a signal configuration 1107, then the MCU server softwareparses and validates the message parameters, which include the assignedlatitude and longitude of the signal, flash color (red or yellow), nameof the traffic flow being controlled by the signal (e.g., “US 93Northbound”), and, if the parameters are found to be valid, saves themto the configuration file and modifies its operations to reflect thecommand parameters 1108.

If the command is a camera assignment command 1109, then the MCU serversoftware parses and validates the message parameters, which includes thename of the camera, the signal to which it is being assigned, and anumeric position that indicates the position of the camera within theset of cameras that may be assigned to the signal, and, if theparameters are found to be valid, saves them to the configuration fileand modifies its operations to reflect the command parameters 1110. Ifthe command is a GPS assignment command 1111, then the MCU serversoftware parses and validates the message parameters, which includes thename GPS source and the signal to which it is being assigned, and, iffound to be valid, saves them to the configuration file and modifies itsoperations to reflect the command parameters 1112, if the command is anLTC command to be relayed to a specific LTC 1113, then the MCU serversoftware parses and validates the message parameters, which include thespecific LTC command, the address of the target LTC, and any parametersused by the particular LTC command, and, if the parameters are found tobe valid, immediately sends the command to the target LTC in a formatconsistent with the transmission medium 1114. In this way, the MCU actsas a proxy for LTC commands, allowing authorized users to send commandsto any LTC via any co-located MCU.

If the command is a vehicle detection message 1115, then the MCU serversoftware parse, and validates the message parameters, which includeeither the name of the camera that generated the command or theidentifier of an LTC for which the message is intended to pertain 1116.If the message parameters are found to be valid, the MCU server softwaredetermines the intended LTC and updates its list of recent vehiclearrivals, which is used, if relevant and as described below, to extendor limit green phase durations through the green idle and auto skipmechanisms. If the command is a skip command 1117, which has noparameters, the MCU server software processes the command 1118 anddetermines whether it is operating in the sequencing mode, and if so,whether current green phase has been active for at least its minimumgreen duration and, if so, immediately advances to the next command inits command sequence and in doing so advances the intersection signalphase or, if the minimum green duration has not been reached, schedulesto advance the intersection signal phase once the minimum green time isreached.

If the command is a hold command 1119, which has no parameters, the MCUserver software processes the command 1120 and determines whether it isoperating in the sequencing mode, and if so, simulates a vehicledetection at each signal in the current green phase, which, depending onthe timing of the command in relation to the command sequence, mayextend the duration of the current green phase by up to the configurablegreen idle time, limited by the configurable maximum green durationtime.

If the command is one of the smart pilot car commands 1121, then the MCUserver software parses and validates the message parameters, whichinclude the command itself (pilot car start or pilot car stop) and takesappropriate action 1122. If the MCU is operating in smart pilot car modeand the lone LTC is in the red phase, a smart pilot car start commandwill cause the MCU, server software to immediately change the lone LTCphase to green and start a countdown timer at the configurable pilot cargreen idle time. If the MCU is operating in smart pilot car mode and thelone LTC is in the green phase, a smart pilot car stop command willcause the MCU seer software to command the lone LTC to cycle to the redphase. Otherwise, no action is taken by the MCU server software. If thecommand is one of the mode change commands 1123, then the MCU serversoftware parses and validates the message parameters, which include thecommand itself (red, flasher, 1-way, sequence, off, or smart pilot car),and takes appropriate action 1124.

Mode change commands will cause the MCU server software to compose a setof LTC commands that will implement the new mode of operation within thecontext of the configuration file and then to replace the list ofcommands in current operation with the newly generated list andimmediately start executing the commands on the list. For the staticmodes, where intersection phase does not change once an initial phasehas been reached (red, flasher, or 1-way), the command list consists ofcommands to bring the individual LTCs to the desired operating mode andthen a repeating set of status commands that are used to ensure that theLTCs remain in the desired operating mode. For the dynamic modes(sequencing and smart pilot car), the command list consists of commandsto bring the LTC or controllers to the desired initial state, followedby a repeating set of commands to sequence the phasing of the LTCs asdescribed by the phase definitions. If the command is not a mode changecommand (or any other command tested thus far), the set of knowncommands having been exhausted, a negative acknowledgement is returnedto the originator 1125, and control is returned to the caller.

FIG. 12 is a flow diagram of the automatic discovery mechanism employedby the MCU to maintain a list of onsite GPS sources, cameras, and LTCs.All LTCs are GPS sources, each LTC may have one or more cameras, andeach is discovered separately. The system maintains a list of allcameras and LTCs that are authorized to work at a given location (e.g.,all LTCs operated by a specific organization). The auto discoveryprocess begins operation 1201 when launched during initialization of theMCU server software. The auto discovery process fetches the list ofauthorized LTCs 1202 and, starting at the beginning of the list,attempts to get the next LTC on the list 1203 and, if successful 1204,requests a status message from the LTC 1205. If this request issuccessful 1206, then the LTC is declared to be active onsite and isincluded in subsequent MCU status messages 1207. The status message isalso scanned for GPS position data and, if found 1208, the LTC is taggedas a source of such data 1209. This process repeats until the list ofauthorized LTCs has been exhausted.

Once that processing is complete, the auto discovery process fetches thelist of known cameras 1210 and, starting at the beginning of the list,attempts to get the next camera on the list 1211. If successful 1212,the auto discovery process attempts to fetch the main page from thecamera's web server 1213. If this attempt is successful 1214, then thecamera is declared to be active and is included in subsequent MCU statusmessages 1215. This process repeats until the list of authorized camerashas been exhausted. Once that processing is complete, the auto discoveryprocess puts itself to sleep for a configurable period of time 1216before starting the next iteration.

FIG. 13 is a screenshot of the MCU's main display page, which isdesigned to display and dynamically update various aspects of the MCU'scurrent configuration and details concerning current and recentoperations. The administrative version of this display contains certaincontrols that the client and public versions do not, and the publicversion contains even fewer controls. The main display page contains thefollowing sub-displays and fields: a program identifier 1; the name ofthe intersection and a general display description 2; the time of themost recently received master control status message, its age and theMCU's time in operation 3; a pre-populated drop-down menu for displayselection 4; a pre-populated drop-down menu for mode change selections5, a display of overall system status, including the MCU identifier,status, mode of operation and source voltage 6; the MCU's currentoperating profile, with phase definitions including phase name, greenmaximum, green minimum, green idle, yellow, and clear durations, as wellas a list of signals belonging to each phase 7; a display of recentsignal phases and vehicle arrivals 8 in strip chart format, with onepair of charts for each signal in the current configuration, each charthaving phase durations and vehicle inter-arrivals times displayed; skipand hold buttons 9 by which an authorized user can influence the timingof signal sequencing without changing the operating mode and potentiallydisrupting intersection operations; a current operations display 10 withone panel for each signal in the current configuration, where each panelcontains an icon representing the signal phase, a button allowing theauthorized user to simulate arrival of a vehicle at the correspondingsignal, and a list of signal status parameters, including name, supplyvoltage, radio link quality, auto/local mode, range from MCU in meters,operating mode of the LTC, vehicle detection counts for the last hourand day, operating temperature within the LTC enclosure, GPS tag andstatus, distance from assigned location, list of cameras assigned to thesignal, and the most recent image from each of the assigned cameras; anda system log area 11 where recent time-stamped system log messages alertthe user to specific recent MCU events.

FIG. 14 is a screenshot of the MCU's map display page, which containsmany common display elements from the main display, with the skip andhold buttons and recent activity display elements replaced with a mapdisplay 12 depicting the geographical locations of the various onsitecameras. LTCs and MCUs, including those under active control of the MCUand those not under its control. For LTCs, compass information is usedto indicate the direction in which the associated signal is pointing.The map display includes markers for each element, which, when clickedupon, will pop up an information box containing information specific tothe display element. The traffic signal state is captured usingiconography from the standard Manual of Uniform Traffic Control Devices(MUTCD).

FIG. 15 is a screenshot of the MCU's setup page, which contains manycommon display elements from the main display, with the central portionof the display replaced with the phase form 13 and onsite signal summary14, which is explained in detail in FIG. 16. The phase form is comprisedof several fields by which the user can define a set of phases and theset of signals belonging to each phase. The user enters values into thefollowing fields for each phase: name, ideally indicating the nature ofthe traffic flow under this phase 15, green phase maximum duration 16,green phase minimum duration 17, green idle time 18, yellow phaseduration 19 and clear phase duration 20, where all signals at theintersection are in red phase simultaneously, allowing the intersectionto clear of traffic before advancing to the next phase.

The user also selects one or more signals (and the associated LTC) to bemembers of the phase 21, where any number of signals may be members, andwhere a signal may be a member of more than one phase (e.g., a signalcontrolling northbound traffic may be a member of a north-south trafficphase as well as a north with protected left turn traffic phase). Theuser specifies each phase, in the desired sequence using one line perphase, with more blank rows being automatically displayed as needed. Inaddition to the phase definitions, the form also contains two fieldsspecific to the smart pilot car mode of operation: maximum greenduration 22 and green idle time 23. Once the user is satisfied with thecontent of the phase form, the save phases button 24 is used to send theform contents to the MCU, where they replace the current configuration.

FIG. 16 is a detailed screenshot of the onsite signal summary displayreferenced in FIG. 15. The summary display is used by the MCU to displaycurrent information regarding all onsite LTCs that may be available forusage, as well as to accept user input regarding the interrelationshipsbetween the components of the system and specific per-signalconfiguration items. The display is organized as a table of rows andcolumns, where each row represents a single LTC, and each columnrepresents some aspect of that LTC's operation or user configurationitem, the list of which includes: a display of the LTC name 25, anyphase memberships 26, various status items including voltage, operatingtemperature, current phase and time in phase 27, vehicle detectioncounts for the last hour and day, and time since the last vehicle wasdetected 28, as well as the following user input fields: flow name 29,auto skip enable/disable 30, flash color selection menu populated withred or yellow selections 31, GPS selection menu populated with knownactive onsite GPS sources 32, a series of generator control buttonsincluding separate enable, disable, run, and stop buttons 33, a seriesof signal control buttons including a vehicle detection simulationbutton, vehicle detection count reset button, start and stop buttons.WiFi enable and disable buttons, and a reboot button 34. In addition,there are two or more camera selection menus 35 and 36, which arepre-populated with all active onsite camera names, and which are used tologically assign cameras to an LTC.

When the user presses any of the generator or signal control buttons onthis portion of the page, corresponding commands are transmitted to theMCU for processing. In addition, when the user makes a selection on theGPS or camera menus, corresponding commands are sent to the MCU with noneed for further interaction. For the remaining fields (flow name, flashcolor, and auto skip enable/disable), the user must press the save flownames button 37 to make those changes active.

FIG. 17 is screenshot of the super remote application of the MCU serversoftware, which provides simplified control of the intersection as awhole and also of the individual LTCs without the contextual status,mapping, and configuration information of the main display. The superremote display includes the following displays and buttons: a banneridentifying the display 38; a sub-header identifying the name of theintersection and the operating mode of the MCU 39; a series of MCU modechanges buttons including a sequence button 40, buttons for one-wayflow, the number of buttons varying with the number of phases defined inthe phase table (41 and 42 in this example); an all red button 43 and aflasher mode button 44; a signal summary section 45 that displays theLTC identifier for each signal, as well as a traffic signal icon (whichalso doubles as a signal selection button) indicating the last reportphase for that signal, with the selected signal outlined in a heavyborder; a header display 46 listing the name of the currently selectedsignal, which signal would be the target of the start or stop buttonaction; a stop button 47, which allows the user to issue a stop commanddirectly to the currently selected signal; a start button 48, whichallows the user to issue a start command directly to the currentlyselected signal; and a display of recent system messages 49 specificallypertaining to the operation of the super remote application.

FIG. 18 is a flow chart of the fixed APS. The APS is a controlapplication with web server functions that allowing it to both acceptcommands from, and return responses to, authorized users and userapplications via a network connection, as well as to perform its controltasks. It is organized as a background loop that repeats for as long asthe computer remains in operation, as depicted on the left in thisfigure, and separate threads that are spawned by the server portion ofthe software in response to network user commands, as depicted on theright in this figure.

At power up 1801, the various electrical components of the APS powerthemselves up, and the APS's operating system bootstraps itself intooperation and eventually starts up the APS. As part of the startupprocess, the server initializes itself 1802 by reading its configurationfiles, which include information about all MCUs and cameras operatingwithin the system. For MCUs, this information includes: MCU identifier,whether the unit is active, its archiving intervals, whether theassociated unit should be watched by the network watcher function(described below), the URL of the unit, an optional customer anddivision tag, as well as a list of contact emails for cognizantpersonnel, for use in generating alert and alarm messages by the watcherfunction. For cameras, this information includes the camera name,whether images from the camera should be periodically downloaded andarchived, delays between image downloads, and URLs for the camera's homepage and for returning a single snapshot.

As part of the initialization process, an archiver is initiated for eachMCU and camera where archiving is enabled. Once initialization iscomplete, the server enters the server loop by first establishing amutual exclusion lock on the data shared with server threads 1803,essentially locking out the network command interface and precludingdata corruption from multiple processes writing to the same storagearea. Once the lock is obtained, the configuration file is re-read 1804,and archivers are added, modified, and deleted as necessary to reflectthe most recent configuration. Once that processing is complete, theindividual archivers are serviced 1805, where completed archive requestsare inserted into the appropriate archive, and where new requests aremade according to dynamic assessments of demand. This process isdescribed in detail in FIG. 19.

Once these processes complete, the APS releases the mutual exclusionlock 1806 and goes to sleep for a brief period of time 1807, allowingexternal users to access to the server. Where a network connectionexists, authorized users can issue network commands directly to the APS.When a user command arrives, the server detects this 1808 and spawns athread to service the request(s) 1809. The first step in processing auser request is to establish a mutual exclusion lock on the sharedserver data 1810. Once the lock is obtained, the APS command is executed1811 and acknowledged, and any requested data is returned to theoriginator. The set of commands recognized by the server is described inFIG. 20. Once command processing completes, the mutual exclusion lock isreleased 1812, and the server thread terminates 1813.

FIG. 19 is a flow diagram of the service archiver function, whereprocessing starts 1901 when it is called from the mainline of the APS.The list of MCUs with active archiving is retrieved 1902, and, if thereare any further MCUs to process 1903, a check is made to determinewhether any status fetches are pending 1904 and, if so, whether thepending fetch has completed 1905. If so, the completion status isaccessed to determine if the fetch was successful 1906. If so, thereceived MCU status message is saved in the archive 1907 and madeimmediately available for retrieval by network users. Once thatprocessing is complete, the delay until the next status request iscalculated 1908, taking into account such factors as baseline samplingrate and current demand for this MCUs status messages from networkusers. If no fetch is pending, a test is made to determine whether it istime for a new status request 1909, and, if so, a fetch of MCU status isinitiated 1910 and a countdown timer started for the completion of thatrequest.

This process iterates until each active MCU archiver has been serviced,at which point the processing moves on to active cameras, where a listof all such active cameras is retrieved 1911. If there are any furthercameras to process 1912, a check is made to determine whether a snapshotfetch for that camera is pending 1913 and, if so, whether the pendingfetch has completed 1914. If so, the completion status is accessed todetermine if the fetch was successful 1915. If so, the received cameraimage is saved in the archive 1916 and made immediately available forretrieve by network users. Once that processing is complete, the delayuntil the next status request is calculated 1917, taking into accountsuch factors as baseline sampling rate and current demand for snapshotsfrom this camera from network users and whether it is day or nightonsite. If no fetch is pending, a test is made to determine whether itis time for a new snapshot request 1918, and, if so, a fetch of asnapshot is initiated 1919 and a countdown timer started for thecompletion of that request. This process iterates until each activecamera archiver has been serviced, at which point control is returned tothe caller 1920.

FIG. 20 is a flow diagram for the processing of APS commands, whereprocessing begins 2001 when it is called from a thread responding torequests from the network interface. If the command is an MCU commandaddressed to a specific MCU 2002, as would be the case for proxy modechange requests, for example, then the command is transformed into anMCU command and transmitted to the intended MCU 2003. An acknowledgementis formulated, acknowledging only that the command has been forwarded tothe addressed MCU, and is returned to the originator 2004, after whichcontrol is returned to the caller 2005. If the command is a request foran archived MCU status message or a snapshot from a camera 2006, thename of the archive is extracted from the request, and the appropriatearchive is accessed for the requested information 2007, after which theinformation is returned to the originator and control returned to thecaller.

If the command is a request for a list of active MCUs 2008, then a listof active master control status archivers is completed 2009 and returnedto the originator and control returned to the caller. If the command isa request for an archive index 2010, then the requested archiver and dayare extracted from the request and a list is constructed of all archiveitems (MCU status messages or camera images) for the specified day 2011and returned to the originator, and control is returned to the caller.The returned archive index items include sufficient timing informationso as to allow user applications to replay MCU displays. Otherwise, anegative acknowledgment is generated 2012 and returned to theoriginator, and control is returned to the caller.

FIG. 21 is a screenshot of an APS consolidated summary application thatdisplays one or more MCU status summaries on a single display, allowingthe user to monitor multiple intersections at once. Each panel of theconsolidated summary display has a similar format, and there may be anumber of such panels in each consolidated summary display. The displaypanel includes the intersection name 50, a summary of the arrival of thelast status message, including its time, age of that time, the timesince the MCU's last startup, the age of the last reported MCU fault,the time duration which the MCU has been onsite, and the unit'soperating mode 51; the display of recent activity 8 (as described inFIG. 13), and a signal summary table 52 containing status informationfrom each signal under control of the MCU and other information such asflow name, LTC identifier, whether a hardware fault is being reported,the operating temperature, link status, supply voltage, time since thelast reported phase change, and the generator control status, if soconfigured.

FIGS. 22A-C are three different screenshots of examples of the stripcharts created by the APS using MCU status messages. FIG. 22A depictsthe reported voltages from a single LTC over the course of three days.FIG. 22B depicts the reported temperature for a single LTC over thecourse of three days. FIG. 22C depicts the radio communication linkquality over the course of three days. The APS is capable of generatingsimilar graphs for other parameters and for arbitrary time periods,dependent upon the contents of its status database.

FIG. 23 is a flow diagram of the network watcher application running atthe NOC. The network watcher is started 2301 at system startup and runsin a loop for as long as the computer is in operation, looking foranomalous conditions and generating alert, alarm, and clear messages asspecific system parameters change over time. At the top of the mainloop, the network watcher determines 2302 whether its Internetconnection status has changed (i.e., is the connection down when it wasmost recently up or up when it was most recently down). If the statushas changed, the Internet connection error status is set or clearedaccordingly 2303. The network watcher then determines 2304 whether theconnection status of the APS has changed (i.e., is the server notreachable when it most recently was and vice versa).

If the status has changed, the APS connection error status is set orcleared accordingly 2305. The network watcher then gets a list of allMCUs being watched 2306, and for each MCU on the list 2307, the mostrecent MCU status message is retrieved and compared 2308 with the nextmost recently received MCU status, several conditions are checked (e.g.,MCU program restart, MCU sequencing errors), and any change in status isnoted 2309. The list of onsite LTCs and their status messages is thenextracted from the MCU status message 2310, and each LTC status message2311 is examined and the system parameters extracted. Among these systemparameters are: supply voltage, operating temperature, radio linkquality, and change in location or pointing direction.

The network watcher then checks 2312 if the alert, alarm, or clearthresholds have been crossed between the two most recent status messagesfor the given LTC, and, if so, the associated error status is updated2313. Once all of the LTCs in an MCU status message have been examined,any new alerts, alarm, or clear messages are consolidated into a minimumnumber of messages 2314. The network watcher then compares the pendingmessages against the list of recently sent messages and, using a set ofpreconfigured lockout intervals between consecutive messages of the sametype, filters out any locked out message. The network watcher thendetermines if any messages are left to send 2315 and, if so, sends thenotifications 2316 via email, SMS text, pager, or any other availablecommunication method. Its processing complete, the watcher the goes tosleep 2317 for a specified period and, upon waking, continues processingat the top of the loop.

FIG. 24 is a flow chart of the MCU's dimming control process, which isresponsible for bringing each of the LTCs under control of the MCU to aknown configured dimming level. Dimming the signal lamps during periodsof low lighting has the twin effect of reducing eye strain onapproaching drivers and greatly reducing power consumption, the latterof which is especially useful for solar-powered systems in that powerdemand is lowered when power supply is at its lowest level. Reducingpower consumption also allows for the use of smaller solar panels andbattery banks, which presents an economic advantage. Upon startup 2401,the dimming mode parameter is accessed, and if the dimming function isturned off 2402, a check is made 2403 to determine if the signals arealready at high power, and, if not, each of the LTCs under command ofthe MCU is commanded 2404 to its high power setting, which is expressedas a percentage of its full power consumption, if the dimming functionis turned on 2405, a check is made 2406 to determine if the signal isalready at low (dimmed) power, and, if not, each of the LTCs under thecommand of the MCU is commanded 2407 to its low power setting, which isexpressed as a percentage of its full power consumption. If the dimmingfunction is set to auto 2408, then the current time is compared to thelocal twilight times 2409. If the current time is before the firsttwilight of the day or after the second twilight of the day (or ifotherwise configured, e.g., based on the ambient light sensor), then acheck is made 2410) to determine whether the signals are at their lowpower level. If not, then the LTCs under command of the MCU arecommanded to their lower power setting 2411. Otherwise, a check is made2412 whether the signals are at their high power level. If not, 2413 thesignals are commanded to their high power setting. If the dimmingfunction is set to auto update 2414, then the early and late localtwilight times are determined 2415 using the signal location as derivedfrom GPS data or another source of the signal location (e.g., user inputor cell tower triangulation). Processing then continues as describedunder 2409. If the dimming function is not set to any of the valuestested above, processing completes 24016.

FIG. 25 is a flow chart of the LTC's dimming control function, whicheffectively dims a set of heterogeneous signal lamps by limiting thepower consumed by each lamp as a percentage of that lamp's maximum powerconsumption. Because the lamps may have different power ratings andefficiencies, dependent upon maker, model, age, and other factors, it isnecessary to vary the power supplied to each lamp independently from allother lamps and to vary it in a way that is unique to that specificlamp. This is done by first measuring each lamp's maximum powerconsumption at its rated voltage and then using the pulse widthmodulation technique to drive the lamp's actual power consumption to thedesired level, measured as a percentage of the lamp's maximum powerconsumption. It should be noted that this approach automaticallycompensates, as it must, for the effects of a discharging battery, whenthe ratio of the pulse width modulation value divided by the deliveredpower starts to rise. The LTC dimming control processing starts 2501several times a second when a check is made 2502 as to whether it isnecessary to recalibrate the first channel, which is done at power upand occasionally thereafter. If it is, a check of the system sourcevoltage is made 2503 to determine whether the power supply issufficiently close to the rated voltage. If so 2504, the first channel'spulse width modulation control is set to the maximum value (100%) and,after a short delay to allow stabilization, the power consumption on thefirst channel measured and saved as the maximum power consumption forthat channel, after which the channel's pulse width modulation is resetto its previous value. In either case, the channel power consumption isthen sampled 2505 at the current pulse width modulation, and this valueis divided by the channel's maximum power consumption, yielding thecurrent dimming ratio. If this ratio is outside the acceptable range2506, then if the usage is too high 2507, the pulse width modulationsetting for this channel is decremented 2508. If not, the pulse widthmodulation setting for this channel is incremented 2509. Once processingis complete for the first channel, a check is made 2510 for any furtherchannels to process. If there are channels remaining, the aboveprocessing is repeated for the next and all subsequent channels. Onceall channels are exhausted, processing is complete 2511.

FIG. 26 is a screenshot of the administrative dialog display of the APSserver software, which provides a method by which geographicallydispersed operators and other authorized administrative personnel canexchange free form text and other messages to record significantoperational events, such as operators logging on and off, changes ofsignal timing, interactions with emergency services, etc. Theadministrative dialog display includes the following displays andbuttons: a banner identifying the display 57; a message display area 58containing columns for the message age 59, time the message entered thesystem 60, user originating the message 61. MCU to which this messagerefers 62, and the content of actual message 63; and an administrativedialog control area 64, which includes a message entry area 65 where anoperator can enter a new message, a send button 66 by which the operatorcan transmit the contents of the message entry area to the APS firarchiving and subsequent real-time display across the operationalnetwork as well as for replay purposes, a show more/less control 67 thatallows the user to display a greater or fewer number of recent messages,a filter control 68 that allows the user to display only recent messagesrelated to a specific MCU or to display recent messages from multipleMCU's, and an acknowledge control 69 by which the user can confirmdisplay of the most recent message and cancel onscreen alerts.

FIG. 27 is a flow chart of the LTC power monitoring process, which isresponsible for detecting power anomalies on the input power channel andall switched output power channels. For safety reasons, it is criticalto know when there are any malfunctions that may cause loss of signallamp efficacy. In addition, because the LTCs may be operated in remoteareas, it is useful to have as much diagnostic information available aspossible about any anomaly. The power monitoring process starts 2701with the sampling 2702 of the first channel's power consumption. If thefirst channel should be powered 2703, then a check is made 2704 whetherthe power is completely off. If it is, then the failure count isincremented 2705 and is then compared against the maximum allowablevalue 2706. If the maximum value has been exceeded, an alarm isgenerated 2707 indicating a complete power fail on the first channel. Ifthe channel power is not completely off, the power is then compared tothe lowest allowable value 2708 and, if lower, the low power count isincremented 2709 and compared against its maximum value 2710. Ifgreater, the power has been below the lowest allowable value too long,and an alarm is generated 2711 indicating low power consumption, perhapsa partially failed lamp, if the channel power is found to be above thelowest allowable value, a check is made 2712 to determine whether thepower is above the highest allowable value and, if higher, the highpower count is incremented 2713 and then compared to its maximum values2714. If greater, an alarm is generated 2715 indicating that the circuitis overloaded. If the channel power is within bounds, a check is made2716 of the channel fail count. If that value is non-zero, then an alarmis generated 2717 indicating that an intermittent connection is likelypresent on the channel. If the channel should be off, a check is made2718 to determine whether the power is in fact off. If it is not, thestuck count is incremented 2719, and then a check is made 2720 todetermine whether the signal has been stuck too long. If so 2721, analarm is generated 2721 indicating that the switch is stuck in the onposition and associated signal lamps may be erroneously on. At thispoint, processing for first channel is complete, and a check is made2722 to determine if more channels remain to be checked. If so, theabove processing is repeated with the second and each subsequent channeluntil the channels are exhausted and processing completes 2723.

FIG. 28 is a flow chart of the alternating single lane traffic algorithmof flow control, which is responsible for providing efficient mutuallyexclusive access to a single traffic lane for vehicular traffictraveling in opposing directions, as depicted in FIG. 3A. To accomplishthis, a demand delay phase is inserted after the traditional sequence ofgreen, yellow, and clear (all red) phases where both signals are held inthe red phase until demand is detected at one of the signals or untilsome maximum time has elapsed. In addition, if a vehicle arrives at asignal during that signal's clear phase and the other signal is idle(i.e., having detected no recent vehicle demand), control will be passedimmediately back to the signal detecting the demand. Processing starts2801 either periodically or in response to a vehicle detection event. Acheck is made 2802 to determine whether either phase has been idlebeyond some maximum time, and, if so, demand is simulated for the idlephase(s). Subsequent to this, a check is made 2803 to determine ifdemand (real or simulated) is registered for phase 1, and if so, a checkis made 2804 to determine if phase 1 is already in the green phase. Ifnot, a check is made 2805 to determine if phase 1 is in the clear phase.If so, a check is made 2806 to determine if phase 2 is idle. If phase 2is idle 2807, control is passed back to phase 1, and a new cycle begins.Otherwise, a check is made 2808 to determine if the intersection is inthe demand delay phase. If so, control is passed hack to phase 1 as in2807. Otherwise, the system is commanded 2809 to skip the next demanddelay phase, as demand on phase 1 is now registered. If demand isinstead registered for phase 2 2810, a check is made 2811 to determineif phase 2 is already in the green phase. If not, a check is made 2812to determine if phase 2 is in the clear phase. If so, a check is made2813 to determine if phase 1 is idle. If phase 1 is idle 2814, controlis passed back to phase 2, and a new cycle begins. Otherwise, a check ismade 2815 to determine if the intersection is in the demand delay phase,and, if so, control is passed back to phase 2. Otherwise, the system iscommanded 2816 to skip the next demand delay phase, as demand on phase 2is now registered. At this point, processing completes 2817.

FIG. 29 is a flow chart for the incremental compass recalibrationfunction, which is responsible for building and maintaining the libraryof calibration samples used to derive the constants required to convertraw compass samples into corrected, or calibrated, azimuth values.Geometrically, the calibration constants to be determined are the x andy coordinates of the center of a circle given x and y points on the edgeof that circle. The conventional approach to compass calibrationinvolves rotating the compass under test, and all affixed ferrousmaterials and magnetic sources, at least one revolution horizontally,all the while sampling the compass iteratively and calculating theaverage of the minimum and maximum observed x and y samples. Thisprocedure is unsafe and impractical for the LTC when installed in itsoperational environment, typically 17 feet above, and cantilevered over,the road surface while mounted to a hydraulically controlledsuperstructure, itself mounted on a stabilized platform. An alternateapproach, described below, is to use standard numerical methods toefficiently estimate the calibration constants by taking a relativelyfew calibration data points under normal operating circumstances.Further, the method provides an incrementally more accurate estimationof the calibration constants by accumulating a progressively larger setof calibration samples. The incremental compass recalibration functionstarts 2901 with a check 2902 to determine it a request to clear thecalibration library has been made, and, if so 2903, the calibrationlibrary is erased, and the calibration constants are set to theirdefault values. A check is then made 2904 to determine whether thecompass is reporting a new location, i.e., one whose raw compass data issignificantly different than any points already in the calibrationlibrary. If so 2905, a new calibration sample is taken from the compassand added to the library, which is stored on some non-volatile mediumand is available at each subsequent power up sequence. At this point,the incremental recalculation of the calibration constants begins when atest is made 2906 to determine if a pair of sample points is availablefor processing. If so, a cord is formed between the points, and a checkis made 2907 to determine if the cord is too short for furtherconsideration due to accuracy concerns, and, if not, a perpendicularbisector to the cord is formed 2908 and saved for future use. Processingcontinues for all unique pairs of compass samples. Processing thencontinues when a check is made 2909 to determine if a pair of uniqueperpendicular bisectors found in 2908 is available and if so, a check ismade 2910 to determine if the two bisectors intersect at too shallow ofan angle for further consideration, due to accuracy consideration. Ifnot, the intersection of the two bisectors is calculated 2911 and savedfor future use, as they are estimates of the calibration constants.Processing continues for each unique pair of bisectors, and then a checkis made 2912 to determine if any intersections were found in 2911. Ifso, an incrementally refined set of calibration constants is calculatedfrom those intersections 2913 and saved for use in future calibratedazimuth computations. A check is then made 2914 to determine if arequest has been made for a calibrated azimuth reading, and, if so 2915,the calibrated azimuth is calculated using the raw compass inputs andthe calibration constants derived in the steps described above. At thispoint, processing completes 2916.

FIG. 30 is a flow chart of the LTC component level control function,which is responsible for providing the MCU and other authorizedapplications and users the ability to reboot or reset individual LTCsystem components while the remainder of the LTC system remainsoperational. While in operation, the LTC cannot be accessed safelywithout disrupting traffic, and so if any of the LTC system componentsbecomes unresponsive or less than completely functional, it is highdesirable that the misbehaving component be addressed singly andremotely, without having to take more the drastic step of manuallycycling power on the LTC itself by physically disconnecting the LTC fromits power supply and then reconnecting. To achieve this, control isperiodically passed to the LTC component level control function, whichstarts 3001 by determining 3002 if a system power cycle has beenrequested. If so 3003, the underlying hardware is commanded to (i) turnoff the electrical supply to all LTC electrical components, except forthat portion of the circuitry required to carry out the power cycle, fora brief period of time sufficient to allow all electrical components toreturn to their quiescent states, and then (ii) reapply power to all LTCelectrical components, remotely simulating the primary remedial actionof unplugging the LTC from power and plugging it back in. At this point,all processing terminates 3004, soon to begin again. If a power cyclehas not been requested, a test is made 3005 to determine if a WiFi resethas been requested. If so 3006, the LTC takes all available actions tobring the WiFi interface and associated hardware to a quiescent stateand then attempts to return them to an operational state. A check isthen made 3007 to determine if a cell modem reset has been requested. Ifso 3008, the LTC takes all available actions to bring the cell interfaceand associated hardware to a quiescent state and then attempts to returnthem to an operational state. A check is then made 3009 to determine ifa reset has been requested for any other interface (e.g., 900 MHz serialradio). If so 3010, the LTC takes all available actions to bring anysuch interface and its associated hardware to a quiescent state and thenattempts to return them to an operational state. A check is then made3011 to determine if a camera reset has been requested. If so 3012, theLTC takes all available actions to bring the indicated camera to aquiescent state and then attempts to return it to an operational state.At this point, processing completes 3013.

FIG. 31 is identical to FIG. 1, except for the addition of two types ofspecialized hardware used to provide motorists advanced warning of thestate of the intersection or of traffic conditions ahead. These twotypes of specialized hardware are operated directly by the LTC via oneor more of its radios and indirectly by the MCU and other authorizedapplications and users via MCU command to the LTC. The first type ofspecialized hardware is a display device 134 of the type readable bypersons in vehicles traveling on a roadway in the vicinity of the systemand capable of displaying text and/or images. The second type ofspecialized hardware is a warning light 135 of the type commonly seen onthe approach to remote and high-speed intersections and that typicallyflashes yellow while the associated signal is in the yellow or red phaseand during the brief interval prior to the lamp turning from green toyellow.

FIG. 32 is identical to FIG. 16, except for the addition of three motionwindow selection columns 70, 71, and 72, each of which is pre-populatedwith the unique names of the motion detection windows present among allcameras under the control of the MCU. These motion detection windowsallow the user to allocate motion detection events to a specific signaland, by extension, to the phases to which the signal belongs. Morespecifically, the user may allocate motion detection events generated bydifferent motion detection windows on a single camera to one or severaldifferent signals and also allocate motion detection events fromdifferent cameras to a single signal. This is useful in situations wherea single camera can detect motion on two or more traffic lanes or whenfor reasons of reliably it is useful to use multiple windows on a singlecamera to detect traffic on the same section of roadway.

FIG. 33 is identical to FIG. 11, with the exception of the addition ofthe jump command, which instructs the MCU to immediately terminate thecurrent traffic phase, jump to the indicated phase, and continuesequencing from there. This is useful for control of intersections withmore than two traffic phases, where a single uninterruptible command isused to influence operations at the intersection, as opposed to usingtwo separate commands, which might leave the intersection in anundesirable state should communications with the MCU be lost between thefirst and second commands of the sequence. Jump processing begins afterprocessing of the hold command when a check is made 1126 to determine ifa jump to a specific phase has been commanded. If so 1127, the MCUrevises its sequence of LTC commands as described above, returns anacknowledgement to the requestor 1103, and terminates 1104.

FIG. 34 is similar to the strip charts in FIGS. 22A-22C except that itdisplays the power consumption over time for a given LTC, including theLTC electronics and all signal lamps controlled by the LTC. This isuseful in absolute terms to compare usage of one LTC to another, andalso in relative terms to determine the usefulness of the dimmingfunction, the impact of which is directly reflected on this chart.

Although the preferred embodiment of the present invention has beenshown and described, it will be apparent to those skilled in the artthat many changes and modifications may be made without departing fromthe invention in its broader aspects. The appended claims are thereforeintended to cover all such changes and modifications as fall within thetrue spirit and scope of the invention.

We claim:
 1. A real-time traffic management system comprising: (a) amain light controller module configured to monitor and controlfunctionality of one or more traffic lights, each traffic lightcomprising a signal head pointing in a direction; (b) a master controlunit server software application that runs on the main light controllermodule; (c) a network watcher application program; wherein the mainlight controller module is configured to communicate with one or morecoordinating light controller modules, onsite personnel, and a networkoperations center; wherein the main light controller module uses acamera that detects instances of vehicle demand and provides live imagesfor situational awareness; wherein the main light controller modulecomprises a global positioning satellite receiver; wherein the mainlight controller module further comprises a light sensor for monitoringambient lighting conditions; and wherein the network watcher applicationprogram continuously scans incoming data, monitors performance of allcomponents in the system, and issues alerts and alarms to notifypersonnel of events or conditions outside of established tolerances. 2.The real-time traffic management system of claim 1, wherein at least oneof the coordinating light controller modules comprises a dimming controlfunction that dims a set of heterogeneous signal lamps.
 3. The real-timetraffic management system of claim 2, wherein each signal lamp in theset of heterogeneous signal lamps has a rated voltage, an actual powerconsumption and a maximum power consumption; wherein the dimming controlfunction measures the maximum power consumption for a given signal lampat the rated voltage and uses pulse width modulation to set the actualpower consumption for the signal lamp to a desired level; and whereinthe actual power consumption is a percentage of the maximum powerconsumption of the signal lamp.
 4. The real-time traffic managementsystem of claim 1, wherein the system further comprises anadministrative dialog display that allows geographically dispersedoperators and other authorized administrative personnel to exchangemessages and record operational events.
 5. The real-time trafficmanagement system of claim 1, wherein each of the coordinating lightcontroller modules has an input power channel and one or more switchedoutput power channels; and wherein the system further comprises aprocess for detecting anomalies on the input power channel and theswitched output power channels of each coordinating light controllermodule.
 6. The real-time traffic management system of claim 1, whereinthe system further comprises a process for controlling alternatingsingle lane traffic.
 7. The real-time traffic management system of claim1, wherein the system further comprises an incremental compassrecalibration function that builds and maintains a library ofcalibration samples used to derive a set of constants required toconvert raw compass samples into calibrated azimuth values.
 8. Thereal-time traffic management system of claim 1, wherein each of thecoordinating light controller modules has at least two components; andwherein the system further comprises a component level control functionthat has the ability to reset an individual component of a lightcontroller module while all other components of the same lightcontroller module remain in an operational state.
 9. The real-timetraffic management system of claim 1, wherein the system furthercomprises a display device readable by persons in vehicles traveling ona roadway and capable of displaying content in the form of text andimages; and wherein the content of the display device is changed inresponse to traffic conditions.
 10. The real-time traffic managementsystem of claim 1, wherein the system further comprises a warning lightthat flashes yellow while an associated signal is in a yellow or redphase and during a brief interval prior to the associated signal turningfrom green to yellow; and wherein the warning light is controlledremotely.
 11. The real-time traffic management system of claim 1,wherein the system further comprises at least one motion detectionwindow that allows a user to allocate motion detection events generatedby different motion detection windows on a single camera to one or moredifferent signals.
 12. The real-time traffic management system of claim11, wherein the at least one motion detection window also allows a userto allocate motion detection events from different cameras to a singlesignal.
 13. The real-time traffic management system of claim 1, whereinthe system further comprises a jump command that instructs the mainlight controller module to terminate a current traffic phase, jump to anindicated traffic phase, and continue sequencing.
 14. The real-timetraffic management system of claim 1, wherein each light controllermodule has a dimming level, and the main light controller module isconfigured to control the dimming levels of the coordinating lightcontroller modules.
 15. The real-time traffic management system of claim14, wherein the main light controller module controls the dimming levelsof the coordinating light controller modules based on time of day. 16.The real-time traffic management system of claim 14, wherein the mainlight controller module controls the dimming levels of the coordinatinglight controller modules based on input from the light sensor.